diff --git a/synapse/events/utils.py b/synapse/events/utils.py
index 824f4a42e3..29ae086786 100644
--- a/synapse/events/utils.py
+++ b/synapse/events/utils.py
@@ -20,6 +20,8 @@ from frozendict import frozendict
 
 import re
 
+from six import string_types
+
 # Split strings on "." but not "\." This uses a negative lookbehind assertion for '\'
 # (?<!stuff) matches if the current position in the string is not preceded
 # by a match for 'stuff'.
@@ -277,7 +279,7 @@ def serialize_event(e, time_now_ms, as_client_event=True,
 
     if only_event_fields:
         if (not isinstance(only_event_fields, list) or
-                not all(isinstance(f, basestring) for f in only_event_fields)):
+                not all(isinstance(f, string_types) for f in only_event_fields)):
             raise TypeError("only_event_fields must be a list of strings")
         d = only_fields(d, only_event_fields)
 
diff --git a/synapse/events/validator.py b/synapse/events/validator.py
index 2f4c8a1018..e0e5bf818c 100644
--- a/synapse/events/validator.py
+++ b/synapse/events/validator.py
@@ -17,6 +17,8 @@ from synapse.types import EventID, RoomID, UserID
 from synapse.api.errors import SynapseError
 from synapse.api.constants import EventTypes, Membership
 
+from six import string_types
+
 
 class EventValidator(object):
 
@@ -49,7 +51,7 @@ class EventValidator(object):
             strings.append("state_key")
 
         for s in strings:
-            if not isinstance(getattr(event, s), basestring):
+            if not isinstance(getattr(event, s), string_types):
                 raise SynapseError(400, "Not '%s' a string type" % (s,))
 
         if event.type == EventTypes.Member:
@@ -88,5 +90,5 @@ class EventValidator(object):
         for s in keys:
             if s not in d:
                 raise SynapseError(400, "'%s' not in content" % (s,))
-            if not isinstance(d[s], basestring):
+            if not isinstance(d[s], string_types):
                 raise SynapseError(400, "Not '%s' a string type" % (s,))
diff --git a/synapse/groups/groups_server.py b/synapse/groups/groups_server.py
index 2d95b04e0c..62d20ad130 100644
--- a/synapse/groups/groups_server.py
+++ b/synapse/groups/groups_server.py
@@ -20,6 +20,8 @@ from synapse.api.errors import SynapseError
 from synapse.types import GroupID, RoomID, UserID, get_domain_from_id
 from twisted.internet import defer
 
+from six import string_types
+
 logger = logging.getLogger(__name__)
 
 
@@ -431,7 +433,7 @@ class GroupsServerHandler(object):
                         "long_description"):
             if keyname in content:
                 value = content[keyname]
-                if not isinstance(value, basestring):
+                if not isinstance(value, string_types):
                     raise SynapseError(400, "%r value is not a string" % (keyname,))
                 profile[keyname] = value
 
diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py
index 4b2b85464d..4650f43029 100644
--- a/synapse/http/matrixfederationclient.py
+++ b/synapse/http/matrixfederationclient.py
@@ -42,6 +42,8 @@ import random
 import sys
 import urllib
 from six.moves.urllib import parse as urlparse
+from six import string_types
+
 
 logger = logging.getLogger(__name__)
 outbound_logger = logging.getLogger("synapse.http.outbound")
@@ -553,7 +555,7 @@ class MatrixFederationHttpClient(object):
 
         encoded_args = {}
         for k, vs in args.items():
-            if isinstance(vs, basestring):
+            if isinstance(vs, string_types):
                 vs = [vs]
             encoded_args[k] = [v.encode("UTF-8") for v in vs]
 
@@ -668,7 +670,7 @@ def check_content_type_is_json(headers):
         RuntimeError if the
 
     """
-    c_type = headers.getRawHeaders("Content-Type")
+    c_type = headers.getRawHeaders(b"Content-Type")
     if c_type is None:
         raise RuntimeError(
             "No Content-Type header"
@@ -685,7 +687,7 @@ def check_content_type_is_json(headers):
 def encode_query_args(args):
     encoded_args = {}
     for k, vs in args.items():
-        if isinstance(vs, basestring):
+        if isinstance(vs, string_types):
             vs = [vs]
         encoded_args[k] = [v.encode("UTF-8") for v in vs]
 
diff --git a/synapse/push/push_rule_evaluator.py b/synapse/push/push_rule_evaluator.py
index 3601f2d365..d55efde8cc 100644
--- a/synapse/push/push_rule_evaluator.py
+++ b/synapse/push/push_rule_evaluator.py
@@ -21,6 +21,8 @@ from synapse.types import UserID
 from synapse.util.caches import CACHE_SIZE_FACTOR, register_cache
 from synapse.util.caches.lrucache import LruCache
 
+from six import string_types
+
 logger = logging.getLogger(__name__)
 
 
@@ -238,7 +240,7 @@ def _flatten_dict(d, prefix=[], result=None):
     if result is None:
         result = {}
     for key, value in d.items():
-        if isinstance(value, basestring):
+        if isinstance(value, string_types):
             result[".".join(prefix + [key])] = value.lower()
         elif hasattr(value, "items"):
             _flatten_dict(value, prefix=(prefix + [key]), result=result)
diff --git a/synapse/rest/client/v1/presence.py b/synapse/rest/client/v1/presence.py
index 4a73813c58..647994bd53 100644
--- a/synapse/rest/client/v1/presence.py
+++ b/synapse/rest/client/v1/presence.py
@@ -23,6 +23,8 @@ from synapse.handlers.presence import format_user_presence_state
 from synapse.http.servlet import parse_json_object_from_request
 from .base import ClientV1RestServlet, client_path_patterns
 
+from six import string_types
+
 import logging
 
 logger = logging.getLogger(__name__)
@@ -71,7 +73,7 @@ class PresenceStatusRestServlet(ClientV1RestServlet):
 
             if "status_msg" in content:
                 state["status_msg"] = content.pop("status_msg")
-                if not isinstance(state["status_msg"], basestring):
+                if not isinstance(state["status_msg"], string_types):
                     raise SynapseError(400, "status_msg must be a string.")
 
             if content:
@@ -129,7 +131,7 @@ class PresenceListRestServlet(ClientV1RestServlet):
 
         if "invite" in content:
             for u in content["invite"]:
-                if not isinstance(u, basestring):
+                if not isinstance(u, string_types):
                     raise SynapseError(400, "Bad invite value.")
                 if len(u) == 0:
                     continue
@@ -140,7 +142,7 @@ class PresenceListRestServlet(ClientV1RestServlet):
 
         if "drop" in content:
             for u in content["drop"]:
-                if not isinstance(u, basestring):
+                if not isinstance(u, string_types):
                     raise SynapseError(400, "Bad drop value.")
                 if len(u) == 0:
                     continue